Based on the LISREL modeling approach for data from monozygotic (MZ) and dizygotic (DZ) twins [Heath et al., 1989; Neale and Cardon, 1992], the hypothesized variance of the logarithm of high density lipoprotein cholesterol due to additive genetic factors was estimated to equal 19% for males.

Unobserved common environment accounted for 32% of the variance of log HDL.

Both estimates controlled for body mass, alcohol consumption, and smoking.